1. Field
A polyamic acid, a polyimide, a method of manufacturing the same, and a polyimide film prepared from the same are provided.
2. Description of the Related Art
As information technology advances and gains popularity, there is an increasing need for an ultralight flexible thin display that consistently consumes a low amount of electrical power. In order to produce a flexible display, a flexible substrate is required; this substrate is the main determinant of performance, reliability and price of a flexible display.
The flexible substrate may include a plastic material, since plastic has easy workability and low weight, and is good for a continuous process. Plastic, however, exhibits low thermal stability. For example, common polyimide films fail to retain their color, and often turn yellow or brown due to heat degradation as a result of a severe thermal history or due to the polymer structure. Such color degradation is generally due to formation of a charge-transfer (CT) complex within or between polymer molecules. This CT complex consists of an electron-giving part, in which a nitrogen atom centers inside the polymer, and an electron-receiving part, in which a carbonyl group centers inside the polymer.
In addition to thermal stability, other properties that are advantageous for a substrate material include a low coefficient of thermal expansion (“CTE”) and high light transmission. In addition, if the plastic substrate is used for an LCD, a lower phase-retardation (“Ro”) is required, in order to achieve wider viewing angles.
Accordingly, there is a need for a polyimide polymer having improved heat resistance, optionally together with other advantageous properties for use in display substrate materials.